This invention relates generally to three-dimensional, high-profile, woven geotextile structures and their method for use in soil retention and stabilization and vegetative reinforcement. More particularly, this invention relates to a generally planar, single-layered homogeneous fabric woven from cross-sectional multi-lobe filament yarns having different heat shrinkage characteristics such that, when heated, the fabric forms a thick three-dimensional, cuspated profile. The multi-lobe filament yarns have a relatively high tensile strength and a relatively high modulus at 10 percent elongation so as to provide a fabric which is greater in strength and more dimensionally stable than other three-dimensional, woven geotextile structures. Such a geotextile fabric is suitable for use on slopes, ditches and other embankments and surfaces where erosion control, soil stabilization and/or vegetative reinforcement may be necessary. The homogeneous, single-component nature of the fabric promotes easier handling and minimizes failure points, while offering a thick, strong and dimensionally stable product upon installation.
Known geotextile products having been used for erosion protection and control include pyramidal fabrics and turf reinforcement mats (TRM's). The latter are typically fabricated in one of the following three ways: (1) polymer monofilament or natural organic fibers are stitch bonded together; (2) polymer monofilament can be fused with netting or (3) polymer monofilaments are woven into erosion control structures. The former include high profile, woven geotextile fabrics.
Woven fabrics having heat-shrinkable yarns incorporated therein are well known. For example, at least three patents to B. H. Foster in the early 1950's (U.S. Pat. Nos. 2,627,644, 2,635,648, and 2,771,661) and one to McCord in 1956 (U.S. Pat. No. 2,757,434) use heat-shrinkable yarns along with non-heat-shrinkable yarns to make honeycombed, puffed and/or corrugated fabrics for use in bedding, clothing and the like.
In addition, woven fabrics having the same or similar general cuspated profile or “honeycomb” type weave configuration as the present invention are known in the art and are used as tower packing and/or as the separation medium in mist eliminators. For instance, Pedersen U.S. Pat. No. 4,002,596 relates to a fluid treating medium through which fluid may pass for removing particulate material from the fluid. The material used is comprised of at least two sets of strands interleaved together in a particular configuration to each other so that the strands extending in one direction are generally straight while the strands extending in another direction are geometrically arranged so as to provide a fabric having a cuspated configuration or profile. The fabric of the present invention is similar in profile except it may bend the strands of yarn in both directions.
Also of major importance to the use of fabrics in soil design and performance are weight, strength, and modulus. It is a combination of these properties, including thickness, which determines whether a geotextile fabric will be suitable for use in soil retention and stabilization as well as turf reinforcement. Desirably, a fabric having a typical tensile strength of at least about 4000×3000 pounds per foot (warp×fill, respectively) as determined by the American Society for Testing and Materials (ASTM) Standard Test Method D6818, a modulus of at least about 10000 pounds per foot determined by ASTM D6818 at 10 percent elongation, is necessary to provide soil stabilization and erosion control on slopes, embankments, subgrades and veneer layers in places such as landfills. While some mattings and other similar structures have, heretofore, been used to aid in soil retention or erosion control, most of these structures have been generally ineffective in providing true stability and reinforcement for the soil. In fact, most of the prior art structures have employed generally straight yarns in at least one direction, are not heat-shrinkable, and/or have filaments which are melt-bonded together so as to cause failure points to exist with respect to the bonding of the fabric.
For example, Daimler et al. U.S. Pat. No. 3,934,421 discloses a matting comprising a plurality of continuous amorphous synthetic thermoplastic filaments which are bonded together at their intersections and can be used for the ground stabilization of road beds.
Murhling et al. U.S. Pat. No. 4,002,034 is directed toward a multi-layered matting for inhibiting the erosion of an embankment around a body of water, the layer closest to the water having less pore space and thinner fibers than the layers away from the water.
Bronner U.S. Pat. No. 4,329,392 discloses a hydraulic engineering matting for inhibiting rearrangement of soil particles comprising a layer of melt-spun synthetic polymer filaments bonded at their points of intersection, a filter layer of fine fibers bonded thereto, and a third layer interdispersed therethrough.
Ter Burg et al. U.S. Pat. No. 4,421,439 discloses a supporting fabric or matting for use on embankments of roads, dikes, and the like. The fabric generally includes straight yarns in both the warp and weft directions with binder yarns extending in the warp direction and woven around the straight yarns of the weft direction. However, these yarns do not impart strength to the straight yarns.
Leach U.S. Pat. No. 4,472,086 is directed toward a geotextile fabric for erosion control having, uncrimped synthetic threads in both the warp and filling directions and a known yarn stitch bonding the warp and filling threads together.
Finally, a commercially known high-profile structure generally used for soil retention and erosion control which does employ heat-shrinkable yarns, but not in a single layer, is disclosed in Stancliffe et al. U.S. Pat. No. 4,762,581. This patent relates to high-profile structures or composites which are noted to be useful as carpet underlay and mattresses as well as embankment stabilization and drainage. These structures are believed to be commercially sold under the trade name, Tensar, and are available from Netlon Limited of Mill Hill, England.
However, the structures in Stancliffe et al. are provided by the welding of a planar, biaxially heat-shrinkable, plastic mesh layer to a planar, relatively non-heat-shrinkable plastic mesh layer at zones which are spaced apart on a generally square grid. Hence, when the heat-shrinkable layer is heated and shrinks, the non-heat-shrinkable layer assumes a generally cuspated configuration with the welded points on the non-heat-shrinkable layer remaining in contact with the heat-shrinkable layer. This patent does not provide a single layer fabric and is susceptible to failure at the welding points bonding the layers together.
Another pyramidal fabric is described in U.S. Pat. Nos. 5,567,087 and 5,616,399, owned by the Assignee of record. The fabrics taught in those patents are woven from round, monofilament yarns and a description of such fabrics and their manufacture is set forth in the aforementioned patents, the subject matter of which is incorporated by reference herein.
Thus, while attempts have been made heretofore to provide a suitable means for stabilizing and retaining soil and for reinforcing turf, the art heretofore has not taught variations to pyramidal fabrics which provide improved revegetation, erosion protection and water quality on slopes and in channels.